1. Field of the Invention
The present invention relates to a portable still camera, and more particularly to a still camera which can photograph high-definition image frames on a silver-salt filmstrip and simultaneously pick up digital image data of each frame through an image sensor.
2. Background Arts
A wide variety of digital still cameras or electronic still cameras have been developed and brought in the market, as IC memories have a higher capacity and getting more compact. The digital still camera picks up a photoelectric image signal from a still image through a solid state imaging device, such as a CCD image sensor, and converts the image signal into digital image data to write it in a memory. The image data written in the memory can be processed in many ways instantly. For example, it is possible to transfer the image data to a peripheral apparatus for image processing like a personal computer, or to a video printer for making a hard copy.
On the other hand, still cameras that photograph still images on silver-salt photo film are well known. In these film-photo cameras, images are photochemically fixed on the photo film that has a higher resolving power even in comparison with the state-of-the-art imaging device with large scale highly integrated pixels. In view of the density gradation and the dynamic range, the silver-salt photo film is superior to the imaging device, so that a high quality still image is obtained by use of the photo film without the need for an expensive camera.
In order to obtain as high of quality image for the digital still camera as available by the film-photo camera, the digital still camera must have a large scale highly integrated imaging device, and a large capacity memory for storing enormous amount of image data that is obtained through the imaging device, i.e. at least 1 megabyte per frame, and 40 megabytes for a 40-exposure filmstrip. As a result, the scale and the cost of the digital still camera are both raised. It may be possible to compress the image data before storing, in order to save the memory capacity. However, once the image data is compressed, it is hard to reproduce the high quality image data from the compressed data even through an advanced image processing.
On the contrary, the film-photo camera can photograph high quality still images at a low cost, but the image on the photo film cannot be directly processed. For the image processing, it is necessary to convert the photographic image into electric image data through an electric viewer or a scanner.
Since a wide spread photo filmstrip can take 12 to 40 frames, an enormous memory capacity is necessary to store image data as an image file in order to maintain the high quality of the image, even while the image data is obtained from a single filmstrip through the scanner or the like. A hard disc or an optical disc, which is incorporated into a personal computer, does not have such an enormous capacity. Although it is possible to store image data of a limited number of designated frames in the memory of the personal computer, all frames on a filmstrip should be scanned to convert them into image data so as to permit designating desired frames. This is inefficient and time consuming. JPB 4-8993 discloses a digital still camera which writes data relating to each image frame, such as the date and the location of photography, along with image data of that frame into a recording medium. But this prior art does not disclose storing image data in association with photographic frames and photo filmstrips.
Meanwhile, a new type of film cartridge, called IX240 type, has been developed and marketed. The IX240 type film cartridge contains a roll of filmstrip whose entire back surface is coated with a transparent magnetic recording layer, so data relating to each frame may be recorded as a binary code on the magnetic recording layer after the exposure. The photo data written on the magnetic recording layer may include a shutter speed and a stop aperture size that are used for taking that frame, the date of photography, and so forth.
It is also known in the art to magnetically or optically record print option data on the filmstrip in association with each frame. The print option data include print format data that assigns a different print format, e.g. a panoramic size print, to one of the image frames that are recorded in the same size on the filmstrip. The print option data may also include the number of prints to be made from an image frame. Conventionally, the print option data is set up prior to exposure, and is recorded after each exposure. Practically, however, it is more useful to determine the print format and the number of prints while observing the photographed image frames after being developed. In addition, the photographer might miss the opportunity of a particular image while setting up the print option data prior to exposure pressing the shutter. Therefore, it is desirable that the camera allows setting up or revising print option data after the film has been exposed while observing the photographed image.